Comparisons between NO2- and O3-sensing properties of phthalocyanines and n-InP thin films in controlled and noncontrolled atmospheres

This paper describes two different semiconductor gas sensors devoted to the detection of oxidizing pollutants in the atmosphere. The first sensor consists of thin films of phthalocyanines as sensing layers (CuPc, ZnF₁₆Pc, and LuPc₂) evaporated onto alumina substrate fitted with interdigitated electrodes. The second sensor is realized with a mineral monocrystalline semiconductor: n-doped epitaxial layer grown on a semi-insulating substrate of indium phosphide. Each sensor has been submitted to low-controlled concentrations of ozone and nitrogen dioxide, and their detection characteristics, such as response time, stability, and sensitivity, are described. Comparison of these two sensors shows their complementary sensing characteristics, and NO₂ and O₃ act in the same way. Measurements under noncontrolled atmosphere (urban air) have been realized and have demonstrated the potentialities of these structures to be used as oxidizing pollutant detectors. Proposed methods to improve the detection of oxidizing species in urban air are discussed.